Gearing

[JT101]

I am looking at purchasing a 36V 1000W motor kit in a few months time. I am currently building the bike it is to go on. However, I am not 100% I'll go for this kit. Maybe something less powerful.

Is there a certain gearing I should choose to match this? I seem to remember reading once that if the gearing isn't high or low enough it makes it harder work.

Thanks

 

[NeilP]

If you want advice on a kit, best you tell us what it is and who from and not just the power and the voltage. There are many many kits that are 36 volt and 1000W.

What you have told us is like saying you are buying a car that is 2 litre, 4 cylinder diesel and are asking for an opinion on it, and asking what tyres to put on it when we have no idea if you plan on driving 800 miles a day or 5 miles off road across muddy fields..

Come on give us some info if you want an answer...Update your profile too, to show where you are

 

[JT101]

Hi Neil

ok, updated my profile.

I can't tell you what it is and who it's from I'm just speculating at the moment.

I can tell you I'll be commuting 14miles each way to work on roads. Skinny tires, full size folding Tern Joe bike.

I'll either go for something small (15mph, 200W), whereby I'll be doing most of the pedal assist to get up to 20mph, or 1000W system, so I can get to 30mph with pedal assist.

I've been looking at Golden Motors, Crystalyte, and various ones on Ebay. Definitely looking at a waterbottle style battery owing to the folding frame.

I'm putting together the bike BEFORE I get the electric kit. If there's anything I can plan for now

As I mentioned, I seem to remember some fella who built a kit and was experimenting with different setups. He changed the number of teeth on the cassette to make it easier to pedal with the motor going i.e. the gear ratio of the cassette.

I can't remember where I read it, and I've never seen anyone else mention it. But I thought I would bring it up to see if it makes a significant difference.

Cheers

 

[torker]

Neil is right about the info needed and the endless possibilites. One thing that jumps out at me is getting 14 mi. range with a waterbottle battery. If that battery is 10 ah lithium and you keep the speed at 20 mph. or less then ok. Keep reading and reading. You will answer all your questions. There are some great deals for complete hub motor kits for around 200 dollars or so. Some even less. As far as gearing if you start with a 36 volt system then most bikes gearing "should" be high enough to keep up pedaling . Most stock kits will run between 15-20 mph. at 36 volts so if you can pedal your bike that fast now you should be ok. Of course once you get electric you might only pedal on hills - if that Welcome btw

 

[NeilP]

If you want to pedal then it is a geared motor you need.
Front mount motor will mean you can leave rear gearing as standard, maybe even build with an internal gear rear hub

 

[andyshirley]

You will probably find that you need high gearing to keep up with the motor and assist the motor to increase the bike speed.

I have a 48tooth big chain ring and I've ordered a dnp 11-28 freewheel. The 14-28 that I have at present isn't quite high enough at times.

I've read that quite a few people have this problem............... but some people will just say learn to peddle faster...... and others don't peddle at all.

 

[d8veh]

Most rear hub-motors have the thread for a free-wheel. On a motor that powerful, you need a 11T top gear otherwise you won't be able to pedal much above 15mph. The best source of them for you would be Cyclezee.com at about £25 plus postage. 48T on the front will allow you to pedal in most situations. 38T/53T double chainrings are quite common on Ebay. They normally fit straight on, but sometimes you have to get a longer BB to stop it touching the chainstay. You don't need a front derailleur. Just keep the chain on the bigger chain-ring, and if you run out of battery, you can hook the chain over with a twig.

You might want to consider the 500w Bafang CST motor, which does about 22mph (continuous real speed) at 36v. You could get more speed by using 12S lipos or 48v battery if that's important for you. The CST takes a cassette, which means much better gearing options where 11T top gear is more normal. I've never seen the CST as part of a Kit so you have to build uour own wheel or get someone to do it for you.

 

[JT101]

Hi, and thanks everyone

Luckily I already have a 48/38/28 Chainring, and a 11-28T 7 speed cassette. Presumably that's what I need.

Assuming I use a pedal assist giving me 15.5mph, and I usually cycle at 10mph without sweating myself, that should get me into the 20's if I combine the two.

So what you're saying is I only use the top chainring, and if I change it to 53T, I can get even higher speeds?

 

[andyshirley]

As long as your controller doesn't cut the motor at a lower speed, yes.

 

[rocwandrer]

Hi, and thanks everyone

Luckily I already have a 48/38/28 Chainring, and a 11-28T 7 speed cassette. Presumably that's what I need.

Assuming I use a pedal assist giving me 15.5mph, and I usually cycle at 10mph without sweating myself, that should get me into the 20's if I combine the two.

So what you're saying is I only use the top chainring, and if I change it to 53T, I can get even higher speeds?

not quite. The motor has to be wound (electrically geared) for the speed you want to go at the voltage you use otherwise the motor will stop delivering power before you reach your goal speed. This is the same as your human power drivetrain needing to be geared to give you a comfortable cadence at the speed you want to go in one of the higher gears.

 

[dogman dan]

Chances are, you'll be able to pedal up to the speed of that motor, if run at 36v, with a 48 t front ring. Likely looking at 25 mph max. Once at full gallop, you will find it hard to pedal up much more speed. 2 mph more is pretty hard, due to increasing wind resistance at speed. But the pedaling is still worth it, because it will extend range if the motor provides 600w, instead of say 700w at full cruise. Your 100w of pedaling , if kept up for one hour, will equal 100wh more capacity battery.

Volt it up, and you might need a big sprocket to keep pedaling. But by 40mph, most of us just hang on rather than pedal.

 

[JT101]

Ok, well I might aswell use what I have. Thanks Dogman, rocwandrer and andyshirley

NeilP mentioned a geared motor. I did a little reading about the pros and cons of geared vs direct drive.

For my application, can I have some preferences from you guys. Again: 14mile commute each way to work. 15mph motor assist, with me providing a light cycle (not breaking a sweat i.e. 10mph normally).

Presumably if I have a geared hub, I shouldn't be using a cassette?

Thanks